The present invention relates to a dual-rod cigarette manufacturing machine.
In particular, the present invention relates to the tobacco shaving devices which operate on the streams of shredded tobacco from which, subsequent to a wrapping operation, the continuous cigarette rods are formed.
On such machines, as described in U.S. Pat. No. 4,336,812 filed by the present Applicant, two streams of tobacco are formed by accumulating tobacco particles underneath respective supports consisting of parallel suction type conveyor belts.
As it travels along the respective said conveyor belt to cigarette forming means, each tobacco stream is subjected to a so-called shaving operation for rendering the thickness of the stream substantially constant.
On single-rod cigarette manufacturing machines, the tobacco shaving devices consist of two identical, coplanar discs, mounted on counter-rotating vertical shafts, having respective cutting edges, and with the discs arranged tangent to each other along the route traveled by the said tobacco stream.
Shaving devices of the aforementioned type, however, are too cumbersome for use on dual-rod cigarette manufacturing machines, the said two streams of tobacco, retained on respective conveyor belts travel only a small distance apart; this distance is imposed by the design of the machine and cannot be increased. To be more precise, if a shaving device of the aforementioned type were to be installed for each of the said two tobacco streams, the disc between the said two conveyor belts would obstruct the path of the second stream, thus preventing it from being fed to the said cigarette forming means.
For this reason, and as described in U.S. Pat. No. 4,304,243 filed by the present Applicant, the shaving devices on dual-rod cigarette manufacturing machines consist of pairs of identical truncated-cone discs, with each disc mounted on an inclined shaft, and the pairs of shafts are downward-converging shafts relative to each other. The said discs present respective tangent cutting edges on the wider ends, and respective generating lines aligned along the route of the respective tobacco stream. Consequently, the discs on each shaving device are inclined downwards in opposite directions from their point of contact with the said tobacco stream, thus preventing any interference with the second stream by the disc facing the same.
The grinding of truncated-cone discs of the aforementioned type, however, has been found to involve serious difficulties as compared with the flat discs employed on single-rod cigarette manufacturing machines.